JPH08263973A - Power source circuit and power supplying method - Google Patents

Abstract

PURPOSE: To suppress useless consumption of battery power in the process of manufacturing VTRs by setting the microcomputer at the service interruption mode when products are in process. CONSTITUTION: When a VTR 10 is under condition of a product in process, the power of battery source 3 is supplied to a power source terminal C2 of a system control microcomputer 5 and an initializing circuit 6. Here, because the output current from the battery source 3 passes a diode D2 and a diode D3, the voltage drop is small and the voltage value of the power source terminal C2, namely, the voltage value of the initializing IC 7 exceeds the value preset at the IC 7. Accordingly the initializing IC 7 switches the initializing signal from the low level to the high level. Because of this, the system control microcomputer 5 detects the voltage value of a voltage detecting terminal C1 after initializing itself. When products are in process, the line power source 2 is not turned on, and the service interruption detecting signal is at 0V, and thereby the system control microcomputer 5 sets the operation mode at the service interruption mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit and a power supply method, and in particular, it is activated by receiving a power supply voltage of one of a line power supply and a battery power supply through a power supply terminal and is activated in accordance with the level of an initialization signal. An initialization signal having one of a first level and a second level is output to the microcomputer that is initialized and is set to the power failure mode according to the voltage value of the line power supply, and the microcomputer according to the terminal voltage value of the power supply terminal. The present invention relates to a power supply circuit for an electronic device including an initialization unit and a power supply method.

[0002]

2. Description of the Related Art Referring to FIG. 4, a conventional video tape recorder (VTR) 1 includes a line power supply 2 of 5.8V and a battery power supply (lithium primary battery) 3 of 3V. The line power supply 2 is connected to the power failure detection terminal C1 of the system control microcomputer 5 via the power failure detection circuit 4, and
The line power supply 2 is connected to the power supply terminal C2 of the system control microcomputer 5 via the diode D1 arranged in the forward direction from the system control microcomputer 5. Further, the battery power source 3 is connected to a power source terminal C2 via a resistor R1 and a diode D2 arranged in the forward direction from the battery power source 3 toward the system control microcomputer 5. Further, the cathodes of the diodes D1 and D2 are grounded via the variable capacitor VC1 and connected to the initialization terminal C3 of the system control microcomputer 5 via the initialization circuit 6.

The diodes D1 and D2 are for preventing the output currents from the battery power source 3 and the line power source 2 from flowing backward, and the resistor R1 is from the line power source 2 when the diode D2 is destroyed. Is for limiting the output current of the. The voltage drops in the diodes D1 and D2 are 0.8 V and 0.2 V, respectively, and a Schottky diode is applied to the diode D2. The variable capacitor VC1 is
This is for removing the ripple of the power supply current and for preventing the instantaneous interruption of the power supply current.

Power failure detection circuit 4 includes resistors R2 and R3 and a variable capacitor VC2. Specifically, the resistor R2
Is inserted between the line power supply 2 and the voltage detection terminal C1,
The resistor R3 is inserted between one end of the resistor R2 and the ground plane,
The variable capacitor VC2 is connected in parallel with the resistor R2. Therefore, the line power supply 2 is connected to the power failure detection terminal C1.
The divided voltage obtained by dividing the power supply voltage of 2 by resistors R2 and R3 is input as a power failure detection signal. If the power failure detection signal does not reach 3.8V, the system control microcomputer 5 sets the operation mode to the power failure mode because it is in the power failure state, and if it is 3.8V or more, it determines that the power failure status is not in the power failure state and sets the operation mode to the normal mode. set. In addition,
When the line power supply 2 of 5.8V is supplied, the level of the power failure detection signal becomes 5.0V.

The initialization circuit 6 includes an initialization IC 7 and a resistor R4.
And the variable capacitor VC2, and the connection point between the resistor R4 and the variable capacitor VC2 is connected to the input terminal of the initialization IC 7. The reset IC 7 outputs an initialization signal of the same level as this terminal voltage to the system control microcomputer 5 if the terminal voltage of the variable capacitor VC3 is 2.4V or more, and outputs an initialization signal of 0V if it is less than 2.4V. To do. The system control microcomputer 5 initializes itself when the level of the initialization signal exceeds 2.4V. The resistor R4 and the variable capacitor VC3 are for controlling the power supply current to secure the delay time. As a result, the initialization IC 7 outputs the initialization signal of the level corresponding to the voltage value after a sufficient time has elapsed since the voltage was applied to the power supply terminal C2.

The system control microcomputer 5 is shown in FIG.
It operates according to the algorithm shown in. That is, first, in step S1, the initialization signal is low level (0V).
If it is low level, step S
In step 3, the initialization flag 8 is set and the process returns to step S1, but if it is not at a high level (2.4 V or higher), it is determined in step S5 whether the initialization flag 8 is set. If "NO" here, the step S is directly executed.
The process proceeds to step 11, but if "YES", step S7
Initializes itself in step S9, and resets the initialization flag 8 in step S9.
Move to In step S11, it is determined whether the line power supply 2 is in the power failure state based on the power failure detection signal provided to the power failure detection terminal C1. Then, if it is in the power failure state, the operation mode is set to the power failure mode in step S13 and the process is ended, but if it is not in the power failure state, the operation mode is set to the normal mode in step S15, and a request from the operator in step S17. Is processed, and the process ends.

When such a VTR1 is manufactured, the battery power source 3
Is supplied. Then, when the VTR 1 is completed, the line power supply 2 is turned on, and the microcomputer 5.
A power supply voltage of 8V is supplied. At this time, as shown in FIG. 6B, the level of the initialization signal becomes 5V, and the system control microcomputer 5 is initialized.
It detects the 5V power failure detection signal shown in (A) and sets itself to the normal mode.

After setting the microcomputer 5 in the normal mode in this manner, an engineer sets a clock (not shown),
Turn off the line power again. Then, the battery power 3 is supplied to the system control microcomputer 5, and the microcomputer 5 operates the clock in the power failure mode. At this time, the voltage applied to the power supply terminal C2, the initialization signal, and the power failure detection signal change as shown in FIGS. 7 (A), (B) and (C).

Therefore, when the user purchases the VTR 1, the clock is already set, and the user does not have to set the clock.

[0010]

However, in such a conventional technique, the system control microcomputer 5 is activated only by the battery power source 3 before the VTR 1 is turned on, that is, before the line power source 2 is turned on. In such a state, there is a problem that a large amount of current flows from the battery power source 3 and the battery power source 3 is consumed. That is, the system control microcomputer 5 starts up when a power supply voltage of 2.2 V or more is applied, but when a large amount of current flows out from the battery power supply 3 at the time of startup, the resistor R1 and the diode D2 generate a voltage higher than that in the power failure mode. In some cases, the system control microcomputer 5 cannot be started due to a drop. Even if it can be started, the power supply terminal C3
The initialization IC 7 may continue to output a low-level signal because the voltage value of 2 is less than 2.4 V, and the system control microcomputer 5 may repeat the processing of steps S1 and SW3 of FIG. In such a case, a larger amount of power than that in the power failure mode is continuously consumed, and the battery power source 3 is exhausted without meaning.

Therefore, a main object of the present invention is to provide a power supply circuit and a power supply method capable of suppressing consumption of a battery power supply as much as possible during the manufacture of electronic equipment.

[0012]

According to a first aspect of the present invention, a power supply voltage of either a line power supply or a battery power supply is received through a power supply terminal, initialized according to an initialization signal, and according to a voltage value of the line power supply. A power supply circuit for an electronic device that includes a microcomputer that is set to a power failure mode and an initialization unit that outputs an initialization signal to the microcomputer according to the voltage value of the power supply terminal. A first diode inserted in the forward direction from the power supply to the power supply terminal; and a series connection of a second diode and a resistance inserted between the battery power supply and the power supply terminal,
Is a power supply circuit including a third diode arranged in the forward direction from the battery power supply to the power supply terminal and further connected in parallel with the resistor and in the same direction as the second diode.

According to a second aspect of the present invention, a power supply voltage of either the line power supply or the battery power supply is received through a power supply terminal, initialized according to an initialization signal, and set to a power failure mode according to the voltage value of the line power supply. A microcomputer, an initialization means for outputting an initialization signal to the microcomputer according to the voltage value of the power supply terminal, a first power supply terminal inserted in the forward direction from the line power supply to the power supply terminal between the line power supply and the power supply terminal. diode,
And a series connection of a second diode and a resistor inserted between the battery power source and the power supply terminal, the second diode being a forward direction from the battery power supply to the power supply terminal. Method (a) If the line power is not turned on to the electronic device, connect the jumper wire in parallel to the resistor,
(b) A method of applying power by removing the jumper wire when turning on the line power to electronic equipment.

[0014]

In the first invention, the first diode prevents the backflow of the battery power supply current to the line power supply, and the second diode
The diode prevents the line power supply current from flowing back to the battery power supply, and the resistor limits the line power supply current flowing back when the second diode is destroyed. When the electronic device is in a work-in-progress state, for example, power of a battery power supply is supplied to the power supply terminal and the initialization means of the microcomputer. At this time, the battery power supply currents are the second and the third.
Since it goes through the diode of, the voltage drop is small and the power supply terminal voltage becomes a predetermined value or more. Therefore, the initialization means is
When the power supply terminal voltage exceeds a predetermined value, the initialization signal is switched from low level to high level, for example. Therefore, after initializing itself, the microcomputer detects the divided voltage value of the line power supply voltage, for example. Since the line power supply is not turned on in the work-in-progress state, this divided voltage value cannot exceed the predetermined value, and the microcomputer sets the operation mode to the power failure mode.

In the second invention, for example, in the work-in-progress state, the battery power supply current passes through the jumper wire and the second diode, so that the voltage drop is smaller than that in the first invention. Therefore, the microcomputer sets the operation mode to the power failure mode as in the first aspect of the invention. After the electronic device is completed, the jumper wire is removed, so that the resistor connected in parallel with the jumper wire performs a desired function.

[0016]

According to these inventions, since the microcomputer is set to the power failure mode in the work-in-progress state, it is possible to suppress the consumption of the battery power source during the manufacturing of the electronic device as much as possible. The above-mentioned objects, other objects, features and advantages of the present invention will become more apparent from the following detailed description of the embodiments with reference to the drawings.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a VTR 10 of this embodiment.
Is a Schottky diode D3 with a voltage drop of 0.2V.
Is the same as the conventional VTR1 shown in FIG. 3 except that it is connected in parallel to the resistor R1 so that the battery power source 3 is directed in the forward direction toward the system control microcomputer 5. Duplicated description will be omitted by attaching reference numerals.

When the VTR 10 is in the in-process state, the output current from the battery power source 3 passes through the diodes D3 and D2 and the system control microcomputer 5 and the initialization IC.
7 given. Therefore, the terminal voltage of the power supply terminal C2, that is, the input voltage of the initialization IC 7 becomes 2.6V as shown in FIG. 2A, and the initialization IC 7 initializes 2.6V shown in FIG. 2B. The signal is output. Therefore,
The system control microcomputer 5 determines whether or not the line power supply 2 is in a power failure state based on the power failure detection signal shown in FIG. In the work-in-progress state, the voltage value of the power failure detection terminal C1 is 0 V, so the system control microcomputer 5 sets the operation mode to the power failure mode. After switching to the power failure mode, the output current from the battery power source 3 becomes minute, so this output current is given to the system control microcomputer 5 via the resistor R1 and the diode D2. At this time as well, the voltage value of the power supply terminal C2 exceeds 2.4 V, so the system control microcomputer 5 continues to maintain the power failure mode.

According to this embodiment, since the system control microcomputer does not consume the power of the battery power source more than necessary, the consumption of the battery power source can be suppressed as much as possible during the manufacture of the VTR. Referring to FIG. 2, the VTR 10 of this embodiment is also the same as the conventional VTR 1 shown in FIG. 3 except that a jumper wire is connected in parallel to the resistor R1 in the work-in-progress state, and thus the same structure as that of the conventional VTR 1 shown in FIG. The same reference numerals are given to the points, and the duplicated description will be omitted.

In the work-in-progress state, the output current of the battery power source 3 passes through the jumper wire 12 and the diode D2.
The voltage of the power supply terminal C2 and the input voltage of the initialization IC 7 are about 2.8V. Therefore, the initialization signal level output from the initialization IC 7 becomes 2.8 V, and the system control microcomputer 5 sets the operation mode to the power failure mode by detecting the 0 V power failure detection signal. V
When TR10 is completed and the line power supply 2 is turned on, the jumper wire 12 is removed and the resistor R1 performs a desired function.

According to this embodiment, the output current of the battery power source 3 passes through the jumper wire 12 to reduce the voltage drop, and the system control microcomputer 5 sets the operation mode to the power failure mode. Can be suppressed as much as possible.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

2A is a waveform diagram showing a voltage value of a power supply terminal, FIG. 2B is a waveform diagram showing an initialization signal, and FIG. 2C is a waveform diagram showing a power failure detection signal.

FIG. 3 is a circuit diagram showing another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional technique.

FIG. 5 is a flowchart showing the operation of the system control microcomputer.

6A is a waveform diagram showing a voltage value of a power supply terminal, FIG. 6B is a waveform diagram showing an initialization signal, and FIG. 6C is a waveform diagram showing a power failure detection signal.

7A is a waveform diagram showing a voltage value of a power supply terminal, FIG. 7B is a waveform diagram showing an initialization signal, and FIG. 7C is a waveform diagram showing a power failure detection signal.

[Explanation of symbols]

 2 ... Line power supply 3 ... Battery power supply 4 ... Power failure detection circuit 5 ... System control microcomputer 6 ... Initialization circuit 10 ... VTR 12 ... Jumper wires D1-D3 ... Diodes R1-R4 ... Resistance

Claims (2)

[Claims] 1. A microcomputer which receives a power supply voltage of one of a line power supply and a battery power supply through a power supply terminal, is initialized in accordance with an initialization signal, and is set in a power failure mode in accordance with the voltage value of the line power supply. And a power supply circuit of an electronic device comprising an initialization means for outputting the initialization signal to the microcomputer according to a voltage value of the power supply terminal, wherein the line power supply is connected between the line power supply and the power supply terminal. A first diode inserted in a forward direction toward a power supply terminal; and a series connection of a resistor and a second diode inserted between the battery power supply and the power supply terminal, The second diode is provided in a forward direction from the battery power source to the power source terminal, and further includes a third diode connected in parallel with the resistor and in the same direction as the second diode. Power circuit. 2. A microcomputer which receives a power supply voltage of one of a line power supply and a battery power supply through a power supply terminal, is initialized according to an initialization signal, and is set to a power failure mode according to the voltage value of the line power supply. An initialization unit that outputs the initialization signal to the microcomputer according to the voltage value of the power supply terminal, and is inserted between the line power supply and the power supply terminal in a forward direction from the line power supply toward the power supply terminal. A first diode, and a series connection of a second diode and a resistor interposed between the battery power supply and the power supply terminal, the second diode extending from the battery power supply to the power supply terminal. A method of applying power to an electronic device in the forward direction, wherein (a) a jumper wire is connected in parallel to the resistor when the line power supply is not turned on to the electronic device, (b) the electronic device A method for applying power, wherein the jumper wire is removed when the line power is turned on.